How to confirm an enumeration to Identifiable protocol in Swift?

Question

I'm trying to make a list with the raw values of the cases from an enumeration with the new SwiftUI framework. However, I'm having a trouble with conforming the 'Data' to Identifiable protocol and I really cannot find information how to do it. It tells me "Initializer 'init(_:rowContent:)' requires that 'Data' conform to 'Identifiable'" The stub provides me with an ObjectIdentifier variable in the last extension, but don't know what should I return. Could you tell me how do it? How do I conform Data to Identifiable, so I can make a list with the raw values?

enum Data: String {
    case firstCase = "First string"
    case secondCase = "Second string"
    case thirdCase = "Third string"
}

extension Data: CaseIterable {
    static let randomSet = [Data.firstCase, Data.secondCase]
}

extension Data: Identifiable {
    var id: ObjectIdentifier {
        return //what?
    }

}

//-------------------------ContentView------------------------
import SwiftUI

struct Lala: View {
    var name: String

    var body: some View {
        Text(name)
    }
}

struct ContentView: View {
    var body: some View {
        return List(Data.allCases) { i in
            Lala(name: i.rawValue)
        }
    }
}

*maybe* this will help : https://stackoverflow.com/questions/24011170/how-to-make-an-enum-conform-to-a-protocol-in-swift — user1105951, Aug 08 '19 at 09:59

Mojtaba Hosseini · Accepted Answer · 2021-05-16T09:20:56.703

49

_{⚠️ Try not to use already used names like Data for your internal module. I will use MyEnum instead in this answer}

When something conforms to Identifiable, it must return something that can be identified by that. So you should return something unique to that case. For String base enum, rawValue is the best option you have:

extension MyEnum: Identifiable {
    var id: RawValue { rawValue }
}

Also, enums can usually be identified by their selves:

extension MyEnum: Identifiable {
    var id: Self { self }
}

Note 1: If you return something that is always unique (each time you call it), like UUID(), this means you get a new object each time you get the object and this will kill reusability and can cause epic memory and layout process usage.

Note 2: From Swift 5.1, single-line closures don't need the return keyword.

Note 3: Try not to use globally known names like Data for your own types. At least use namespace for that like MyCustomNameSpace.Data

Inline mode

You can make any collection iterable inline by one of it's element's keypath:

For example to self:

List(MyEnum.allCases, id:\.self)

or to any other compatible keypath:

List(MyEnum.allCases, id:\.rawValue)

edited May 16 '21 at 09:20

answered Aug 08 '19 at 11:30

Mojtaba Hosseini

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Could you elaborate on why a UUID will degrade performance? – Peter Kaminski Apr 22 '21 at 11:05
It will not! returning **A NEW** UUID each time will force the engine to build a brand new component instead of reusing the old one. – Mojtaba Hosseini Apr 22 '21 at 15:42
Got it, thanks for clarifying. Is there any documentation on how the id that's passed in is used by SwiftUI to determine if a view needs to be invalidated/created/recreated? – Peter Kaminski Apr 22 '21 at 15:45
The id must be unique **per** unique data. You just pass the data and let the render engine decide whether it needs an invalidated/created/recreated object. I think you should search around "List" and "identifier" and their documentations. – Mojtaba Hosseini Apr 22 '21 at 16:03

score 0 · Answer 2 · answered Dec 25 '20 at 05:15

0

You can try this way:

enum MyEnum: Identifiable {
    case valu1, valu2
    
    var id: Int {
        get {
            hashValue
        }
    }
}

answered Dec 25 '20 at 05:15

Olcay Ertaş

5,374
8
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How to confirm an enumeration to Identifiable protocol in Swift?

2 Answers2

Inline mode